The present invention relates to vehicles in general, and more particularly to a pedal-driven vehicle.
There are already known various constructions of pedal-driven vehicle, such as bicycles, tricycles and mopeds, which usually include a frame, a plurality of wheels rotatably mounted on the frame, a pedal arrangement including a driving gear and rotatably supported in a pedal shaft bearing mounted on the frame, a driven gear mounted on the hub of one of the wheels for rotation therewith, and an elongated endless transmission element trained about and interconnecting the driving and driven gears. The frame usually includes a rearwardly arranged saddle tube which extends upwardly and slightly rearwardly from the pedal shaft bearing, a lower frontward frame tube extending inclinedly frontwardly from the pedal shaft bearing, a steering sleeve mounted on the upper region of the lower frontward frame tube, and a connecting structure which is arranged above the lower frontward frame tube at a distance therefrom and interconnecting the steering sleeve with the saddle tube.
In such pedal-driven vehicles, such as bicycles, there is usually used a chain transmission for transmitting the driving force exerted by the bicycle rider from the pedals to the rear wheel. Such chain transmissions initially have an efficiency of about 95%. However, this efficiency soon decreases, due to insufficient lubrication and as a result of wear to about 70%. The chain requires a certain degree of maintenance during its use; more particularly, it must always be well lubricated. As a result of this, the chain always constitutes a cause of soiling for the bicycle rider, which is especially disadvantageous if the chain has slid off from one or both of the gears and must be manually placed on the driving and driven gears. However, even during the normal operation of the bicycle, the legs or trousers of the bicycle rider may become soiled by the chain lubricant.
To the extent that the pedal drive of such pedal-driven vehicles includes a toothed belt instead of a chain, there exists the disadvantage that, when strongly pulsating tensional forces are encountered in the toothed belt, such as during the start-up or the braking operation, there may occur a so-called treading through or jumping over of the toothed belt. During this operation, there occurs withdrawal of the teeth of the toothed belt from the spaces between the teeth of the driven gear during vigorous pedaling. Herein, the teeth of the toothed belt ultimately reach the crests of the teeth of the driven gear and then slide over such crests and fall into the spaces between the respectively following teeth of the driven gear. Thus, there occurs an operation which is reminiscent of slippage.
An increase in the width of the toothed belt and of the gears is not of any interest for space reasons, inasmuch as a drive which is as thin as possible is desired in bicycles. Even the use of a pressing roller which engages the toothed belt from the outside at the input region to the driven gear, as it is shown in the U.S. Pat. No. 4,099,737, does not bring about satisfactory results.
Moreover, if the connecting structure extends from the steering sleeve to the lower region of the saddle tube, as it does in the so-called ladies' bicycles, so that the frame has a substantially V-shaped configuration at its region located between and underneath the saddle and the handlebars so as to present upwardly of the pedal drive a mounting space which is not present in the so-called men's bicycle having a horizontal upper bar extending between the steering sleeve and the upper region of the saddle tube, the stiffness of the frame is rather low, so that it can be relatively easily deformed.